"Writing and Running a Simple 'Hello, World!' Program in x86-64 Assembly on Fedora Linux"

asm.md

Below is a simple "Hello, World!" program written in x86-64 assembly language for Linux. I'll also provide instructions on how to assemble, link, and run it on Fedora Linux.

Hello World Assembly Code (x86-64)

Save the following code in a file named hello.asm:

section .data
    hello db 'Hello, World!', 0x0A  ; 'Hello, World!' followed by a newline (0x0A)

section .text
    global _start

_start:
    ; Write 'Hello, World!' to stdout
    mov eax, 1          ; syscall: sys_write
    mov edi, 1           ; file descriptor: stdout
    lea rsi, [hello]     ; address of the string to write
    mov edx, 14          ; length of the string (13 characters + 1 newline)
    syscall              ; invoke the system call

    ; Exit the program
    mov eax, 60          ; syscall: sys_exit
    xor edi, edi         ; exit code: 0
    syscall              ; invoke the system call

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Instructions to Assemble, Link, and Run on Fedora Linux

1. Install the necessary tools (if not already installed): You need nasm (Netwide Assembler) and ld (GNU linker). Install them using dnf:

   sudo dnf install nasm binutils

2. Assemble the code: Use nasm to assemble the hello.asm file into an object file:

   nasm -f elf64 hello.asm -o hello.o

   This generates an object file named hello.o.

3. Link the object file: Use ld to link the object file into an executable:

   ld hello.o -o hello

   This creates an executable file named hello.

4. Run the program: Execute the program using:

   ./hello

   You should see the output:

   Hello, World!
   

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Explanation of the Code

• .data section: Contains the string Hello, World! and a newline character (0x0A).
• .text section: Contains the program's instructions.
• _start: The entry point of the program.
• System calls:
  • sys_write (eax = 1): Writes the string to stdout.
  • sys_exit (eax = 60): Exits the program with a status code of 0.

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